In general, a power distribution system is configured from a high voltage system (e.g., 3300 volts to 6600 volts) and a low voltage system (e.g., 100 volts to 200 volts). Power receiving ends of general consumers are connected to the low voltage system. Power companies are obligated to maintain the voltage at the power receiving ends of the general consumers within a proper range (e.g., in the case of power reception of 100 volts, the voltage is maintained at 95 volts to 107 volts). Therefore, the power companies attain the voltage maintenance at the power receiving ends of the general consumers by adjusting the amount of control of voltage control apparatuses (e.g., LRTs (Load Ratio Control Transformers) or SVRs (Step Voltage Regulators)) connected to the high voltage system (e.g., by operating taps). Note that, in the following explanation, the power distribution system indicates the high voltage system thereof unless specifically noted otherwise.
Conventionally, concerning the voltage control of the power distribution system, a local voltage control device integrated or juxtaposed with a voltage control apparatus of a transformer type such as an LRT or an SVR is widely spread. The local voltage control device performs, in an autonomous distributed manner, voltage control of the voltage control apparatus on the basis of measurement information (a voltage and a power flow) near the setting point of the voltage control apparatus. Note that, as the voltage control apparatus, besides the voltage control apparatus of the transformer type, there has been known a voltage control apparatus of a reactive power control type such as a phase modification facility (a phase advance capacitor, a branch reactor, etc.) having a function of automatically switching between operation and non-operation, an SVC (static Var Compensator), or a PCS (Power Conditioning System) with a reactive power adjusting function is known. Local voltage control devices respectively corresponding to these voltage control apparatuses are also in the stage of practical use. The PCS is, for example, a power conditioner for solar power generation and connects a solar power generation facility or a storage battery and a power distribution system.
These local voltage control devices are configured on the premise that fluctuations in load distribution of the power distribution system are uniform, that is, the voltage at each power distribution system point changes in the same direction over time. However, in recent years, for example, with the diversification of the ways of using electricity and the spread of distributed power supplies due to solar power generation and the like, the load distribution of the power distribution system tends to non-uniformly and largely fluctuate over time. Therefore, it is becoming difficult to maintain a proper voltage with the voltage control of the conventional power distribution system.
Therefore, instead of the voltage control system of the autonomous distribution type, it has been proposed to provide centralized control of the voltage of the power distribution system in a consistent form over the entire system (a centralized control system). Specifically, a mechanism has been proposed in which measurement information (voltages and power flow) at a plurality of points in the power distribution system is collected in a centralized voltage control device using a dedicated network, the centralized voltage control device determines the amount of control (reactive power, etc.) of each voltage control apparatus on the basis of these pieces of measurement information, and the centralized voltage control device automatically and remotely issues a command regarding the amount of control to each voltage control apparatus (see, for example, Patent Literature 1).